The invention relates to a method for controlling a cycloconverter which is designed to connect a first three-line network to a second three-line network. The cycloconverter has six converter branches connected in series with energy stores, wherein the converter can be controlled so that energy transfer from the first three-line network into the second three-line network or vice versa can occur in accordance with energy demand, energy supply and/or reactive power criteria. The invention further relates to an electronic control device for such a cycloconverter, a cycloconverter and also computer programs for controlling a cycloconverter.
In general the invention relates to the control of a cycloconverter in what is referred to as a hexverter configuration, i.e. in a configuration in which six converter branches are connected in series and the total of six lines of the first and of the second three-line network are each switched at the connection point between two converter branches. Such a configuration of a modular cycloconverter has already been proposed in the unpublished application DE 10 2010 013 862. Such a hexverter has the advantage that, by comparison with conventional matrix arrangements consisting of nine converter branches, the required module number and thus the hardware outlay can be reduced by a third, without this resulting in adverse effects on the performance. Compared to back-to back arrangements (M2LC topology) with 12 converter branches the number of modules can even be halved.
Some or all of the individual converter branches in such cases can have electrical energy stores, e.g. in the form of capacitors or rechargeable batteries (accumulators). A converter branch in such cases can be embodied from a single bridge module for example, as will be explained in greater detail below with reference to the exemplary embodiments. Series circuits of such bridge modules are also advantageous for forming a converter branch, since benefits will be obtained in respect of the regulation options, redundancy and the harmonic content of the output voltages and currents. The term “converter branch” therefore encompasses a single bridge module or a series circuit of a number of bridge modules.
The cycloconverter in the form of a hexverter explained here is novel, so that there is a desire for control of the hexverter which is as efficient as possible. Known methods of controlling cycloconverters are optimized to other circuit topologies.